President Obama declares a new counter-terrorism partnership with the country, already battling poverty and a civil war. Gen. David H. Petraeus arrives there to announce new aid.

Reporting from Washington — As the war on terrorism turns toward the Al Qaeda threat from Yemen, U.S. intelligence officials say that the country's strategic location, lawlessness and instability may make it an even more problematic battleground than Pakistan or Afghanistan.

The impoverished nation, already struggling with civil war, has become a far more inviting haven for Al Qaeda fighters than even Afghanistan before the Sept. 11 attacks, the officials say.

The severity of the threat -- and the United States' deepening involvement -- were underscored by President Obama on Saturday as he declared a new counter-terrorism partnership with Yemen that will include more intelligence-sharing, training and possibly joint attacks against the rising Al Qaeda affiliate in the region, known as Al Qaeda in the Arabian Peninsula.

Obama's top commander in Iraq and Afghanistan, Gen. David H. Petraeus, arrived in Yemen on Saturday to meet with President Ali Abdullah Saleh and announce that the U.S. will sharply increase its counter-terrorism aid in the coming year.

The Yemeni government also deployed hundreds of troops into the mountainous Mareb province and other Al Qaeda strongholds as a show of its commitment.

Obama, offering new details on the attempted Christmas Day bombing of a Detroit-bound airliner, said that the Yemen branch of Al Qaeda trained, equipped and dispatched the 23-year-old Nigerian man accused of trying to blow up the Northwest Airlines plane.

The rise of Al Qaeda in Yemen is, in part, a product of the country's central location. It lies at the heart of the Arab world and is far more hospitable than other militant strongholds in South Asia and Africa, where Arab operatives stick out from the locals.

But added to the combustible mix is a weak government that successive U.S. administrations have accused of being corrupt and reluctant -- at best -- to go after Al Qaeda. That has been the case not only in the country's chaotic expanses, but also in the capital, where U.S. officials believe Yemeni authorities have aided numerous suspicious jailbreaks and outright releases of detained senior Al Qaeda members.

The result has been an intense -- and mutual -- distrust between Washington and Yemen's capital, Sana, that has limited economic aid to a trickle, further complicating efforts to combat terrorist cells.

A senior Yemeni official cautioned that even the new military aid will not quickly alter the situation since it would take months, if not years, to produce results.

"It takes time to order the equipment and set up the programs," he said.

While the group in Yemen still lacks the training and recruiting infrastructure to become as dangerous of a global threat as the "core" Al Qaeda along the border of Pakistan and Afghanistan, U.S. officials believe it may be only a matter of time.

"If left unaddressed, that will happen," said Kenneth Wainstein, President Bush's top counter-terrorism advisor. "It is right there in the middle of everything, and right where Al Qaeda wants to be, on the Arabian peninsula, near Mecca" -- the Saudi Arabian city that is Islam's holiest place.

The ancestral homeland of Osama bin Laden, Yemen has long been a haven for a small group of Al Qaeda fighters, including the suicide bombers who blew a hole in the U.S. destroyer Cole in October 2000, killing 17 sailors.

U.S. officials said those cells had largely been dismantled after the Sept. 11, 2001, terrorist attacks with the intermittent cooperation of the Yemeni government.

But they have returned in recent years, along with new fighters that include battle-hardened veterans from Iraq, Afghanistan, Pakistan, Somalia and neighboring Saudi Arabia, as well as detainees released from Guantanamo Bay, Cuba, senior administration and intelligence officials say.

Over the last two years, those officials say, the cells have coalesced into a well-equipped and well-funded network capable of launching many more attacks in Yemen and the region.

The growing capabilities and aspirations of the network were demonstrated in the Christmas Day bombing attempt. The suspect, Umar Farouk Abdulmutallab, had studied in the country and had been in contact with Al Qaeda leaders there.

Al Qaeda in the Arabian Peninsula later claimed responsibility for the attempt.

U.S. officials are also growing concerned about the increasing power of clerics in Yemen to recruit and radicalize Muslims worldwide. American-born cleric Anwar al Awlaki is believed to be a key player in the Al Qaeda affiliate.

The FBI is investigating connections between Awlaki and both Abdulmutallab and Maj. Nidal Malik Hasan, the U.S. Army psychiatrist accused of killing 13 at Ft. Hood, Texas, in November.

Yemeni clerics are also believed to have influenced Abdulhakim Mujahid Muhammad, a Muslim convert who lived in Yemen before allegedly shooting two soldiers at a U.S. Army recruiting center in Little Rock, Ark., last June, killing one of them.